5G 
Records of the Geological Survey of India. 
[VOL. VIII. 
2. These features are directly connected with the rock-structure. The well known 
, geographical name for the southern crest of elevation has been 
Structure. i c 
adopted for the great sedimentary formation which forms the basis 
of the whole plateau. Except along the edges of their ai’ea, the Vindhyan strata are hori¬ 
zontal ; and this arrangement, combined with alternations of hard and soft rocks, induces the 
fiat scarped form of elevation. In the south-west part of the plateau in Malwa, where the 
Vindhyans are so completely covered by eruptive rocks, the same form of elevation is 
constant, illustrating admirably the step-like arrangement for which the name of trap-rock 
was originally given to these ancient volcanic products. 
3. To proceed in regular order from the youngest to the oldest formations, brief notice 
_ .. must be taken of the superficial deposits. There is little or no 
Superficial deposits. . . 1 r 
alluvium proper m this country, actual land-formation now in 
progress from river deposits; unless we are to include under this head the almost ceaseless and 
everywhere present action of wind and rain in shifting and arranging the earth particles 
at the surface. The soil and subsoil covering is on the whole inseparable from the thick 
accumulations of clays, sands and gravels occurring over the plains and valleys; although 
the great depth of these and their forming steep banks high over the extreme flood level of 
the great rivers, clearly point to conditions of formation separated from the present by 
marked physical changes, involving a lowering of the water-level in this region. In confirm¬ 
ation of this observation, we find these deposits continuous with those of the great Gangetic 
plains, in which the remains of extinct varieties of large mammals have been found. The 
best known locality for these fossils is near Etawa in the bed of the Jamuna, close to the 
north-east limit of Scindia’s territory. It is very likely that similar remains might be found 
within the boundary in the Chambal and other large streams. 
4. The trap-rock of Malwa is the next in order of ago to the valley-deposits, the break 
, in time between them being enormous, embracing nearly the whole 
The Deccan trap. . , ° a j 
of the geological period known as tebtiaby. The formation is 
known as the Deccan trap, this rook in Malwa being in unbroken connection across the 
valleys of the Narbada and the Tapti, with that forming the great plateau of the Deccan. 
The upper limit of age for the formation is given by the occurrence of nummulitic strata 
resting upon a denuded surface of the trap along the western base of the highlands near 
Broach. The lower limit of age is fixed by the occurrence of cbetaceous rocks, supposed 
to be middle cretaceous, beneath the trap at Bagh in one of Sciiulia’s outlying districts in 
the Narbada valley, and also on the plateau near Jabna. Within the formation itself there 
occur local intertrappean beds, patches of sedimentary rock, earthy and calcareous, frequently 
containing freshwater fossils. The independent evidence of these has been thought to connect 
the trap more with the tertiary than with the secondary epoch. The trap belongs to the 
basaltic family, hut presenting many varieties from greenish black, dense, columnar basalt, to 
porous amygdaloids with agates and zeolites, and to earthy ash-like beds. Within the district 
under notice no dykes have been observed, showing that it is beyond the immediate region of 
eruption. The present northern limit of the trap is an irregular line between Nhnaeli and 
Badrawas, It is purely a boundary of denudation, and it would be impossible to say how 
much farther to the north the eruptive rock may originally have extended. The laterite 
band which is so generally associated with the trap may give a clue to this question. There 
are many kinds of laterite of different ages and modes of origin. The variety here spoken of 
is a purely earthy ferruginous rock free from sandy detritus, its upper part, to a depth of 
ten to twenty feet, being intensely hardened by the segregation of the iron. It appears as 
a capping to the highest plateau of the trap, thus having the apparent relation of an original 
